Tower microneedle minimizes vitreal reflux in intravitreal injection

Hollow microneedles for ocular drug delivery

Microneedles (MNs) are micron-sized needles, typically <2 mm in length, arranged either as an array or as single needle. These MNs offer a minimally invasive approach to ocular drug delivery due to their micron size (reducing tissue damage compared to that of hypodermic needles) and overcoming significant barriers in drug administration. While various types of MNs have been extensively researched, significant progress has been made in the use of hollow MNs (HMNs) for ocular drug delivery, specifically through suprachoroidal injections. The suprachoroidal space, situated between the sclera and choroid, has been targeted using optical coherence tomography-guided injections of HMNs for the treatment of uveitis. Unlike other MNs, HMNs can deliver larger volumes of formulations to the eye. This review primarily focuses on the use of HMNs in ocular drug delivery and explores their ocular anatomy and the distribution of formulations following potential HMN administration routes. Additionally, this review focuses on the influence of formulation characteristics (e.g., solution viscosity, particle size), HMN properties (e.g., bore or lumen diameter, MN length), and routes of administration (e.g., periocular transscleral, suprachoroidal, intravitreal) on the ocular distribution of drugs. Overall, this paper highlights the distinctive properties of HMNs, which make them a promising technology for improving drug delivery efficiency, precision, and patient outcomes in the treatment of ocular diseases.

Current Insights into Targeting Strategies for the Effective Therapy of Diseases of the Posterior Eye Segment

The eye is one a unique sophisticated human sense organ with a complex anatomical structure. It is encased by variety of protective barriers as responsible for vision. There has been a paradigm shift in the prevalence of several major vision threatening ocular conditions with enhanced reliance on computer-based technologies in our workaday life and work-from-home modalities although aging, pollution, injury, harmful chemicals, lifestyle changes will always remain the root cause. Treating posterior eye diseases is a challenge faced by clinicians worldwide. The clinical use of conventional drug delivery systems for posterior eye targeting is restricted by the ocular barriers. Indeed, for overcoming various ocular barriers for efficient delivery of the therapeutic moiety and prolonged therapeutic effect requires prudent and target-specific approaches. Therefore, for efficient drug delivery to the posterior ocular segment, advancements in the development of sustained release and nanotechnology-based ocular drug delivery systems have gained immense importance. Therapeutic efficacy and patient compliance are of paramount importance in clinical translation of these investigative drug delivery systems. This review provides an insight into the various strategies employed for improving the treatment efficacies of the posterior eye diseases. Various drug delivery systems such as systemic and intraocular injections, implants have demonstrated promising outcomes, along with that they have also exhibited side-effects, limitations and strategies employed to overcome them are discussed in this review. The application of artificial intelligence-based technologies along with an appreciation of disease, delivery systems, and patient-specific outcomes will likely enable more effective therapy for targeting the posterior eye segment.

Microneedles for advanced ocular drug delivery

In the field of ocular drug delivery, topical delivery remains the most common treatment option for managing anterior segment diseases, whileintraocular injectionsare the current gold standard treatment option for treating posterior segment diseases. Nonetheless, topical eye drops are associated with low bioavailability (<5%), and theintravitreal administration procedure is highly invasive, yielding poor patient acceptability. In both cases, frequent administration is currently required. As a result, there is a clear unmet need for sustained drug delivery to the eye, particularly in a manner that can be localised. Microneedles, which are patches containing an array of micron-scale needles (<1 mm), have the potential to meet this need. These platforms can enable localised drug delivery to the eye while enhancing penetration of drug molecules through key ocular barriers, thereby improving overall therapeutic outcomes. Moreover, the minimally invasive manner in which microneedles are applied could provide significant advantages over traditional intravitreal injections regarding patient acceptability. Considering the benefitsofthis novel ocular delivery system, this review provides an in-depth overviewofthe microneedle systems for ocular drug delivery, including the types of microneedles used and therapeutics delivered. Notably, we outline and discuss the current challenges associated with the clinical translation of these platforms and offer opinions on factors which should be considered to improve such transition from lab to clinic.

Can Vitreous Reflux Affect The Short-Term Treatment Response After Intravitreal Ranibizumab Injection?

PURPOSE

The aim of this study was to evaluate the effect of vitreous reflux (VR) on the short-term effect of intravitreal ranibizumab injection.

MATERIALS AND METHODS

The study included 181 eyes of 81 age-related macular degeneration (AMD) and 100 diabetic macular edema (DME) patients. Treatment response was evaluated by measuring central macular thickness (CMT) as well as 1 mm and 3 mm central macular thicknesses (MT1 and MT3). Patients were grouped as; Group 1: no VR, Group 2: <3 mm VR, and Group 3: >3 mm VR according to conjunctival bleb diameters. The data were analyzed using variance, correlation and regression analyses.

RESULTS

In AMD patients, reduction of CMT values following the treatment were 88.3 ± 110.6 µm in Group 1, 85.6 ± 158.7 µm in Group 2, and 93.1 ± 92.2 µm in Group 3. Likewise, in DME patients, it was 82.4 ± 88.4 µm, 72.9 ± 109.9 µm, and 73.7 ± 113.7 µm, respectively. Reduction of MT1 values after the treatment were 47.4 ± 72.6 µm, 36.0 ± 131.9 µm, and 36.7 ± 114.4 µm in AMD patients, and 33.3 ± 72.5 µm, 36.6 ± 90.2 µm, and 46.9 ± 83.4 µm in DME patients. In all comparisons among groups of VR, macular thickness (MT) change did not exhibit significant difference following an intravitreal ranibizumab treatment (p > .05).

CONCLUSION

We found that the increase in VR amount did not adversely affect the decrease in MT after intravitreal ranibizumab treatment in AMD and DME patients.

Applications of microneedles in delivering drugs for various ocular diseases

Treatment of majority of eye diseases involve the use of eye drops or eye ointments, which have major drawbacks of needing frequent administration, lower bioavailability and inability to cross the various eye barriers. This necessitates the use of novel delivery systems. Microneedles (MNs) as an alternate novel delivery system facilitate drug delivery to various ocular diseases with promising approaches in healthcare. Advances in pharmaceutical technology have made MNs provide localized, effective, less invasive and targeted drug delivery in the eye. The purpose of this review is to provide an insight to efficacious therapeutic applications the MNs can bring in various ocular diseases. Out of which, glaucoma, age-related macular degeneration, uveitis, retinal vascular occlusion and retinitis pigmentosa are majorly discussed. Among the various types of MNs; solid coated, hollow and dissolving polymeric MNs are specifically focused for their applications in ocular diseases. In addition, MNs shows improvement in the visual acuity and decreases the progression of the different ocular diseases.

Major factors affecting intraocular pressure spike after intravitreal ranibizumab injection: Vitreous reflux and its amount

PURPOSE

The aim of this study was to assess the effect of vitreous reflux and its amount on short-term intraocular pressure after intravitreal injection of ranibizumab.

METHODS

The study included 316 eyes of 276 patients. Intraocular pressures were measured before intravitreal injection (preIOP), immediately after intravitreal injection (postIOP0), and 30 min after intravitreal injection (postIOP30). The amount of vitreous reflux was evaluated by measuring conjunctival bleb diameter, and patients were grouped as; group 1: no vitreous reflux, group 2: less vitreous reflux, and group 3: more vitreous reflux. The data were analyzed using variance analysis, chi-square test, and regression analysis.

RESULTS

PostIOP0 values were highest in group 1, followed by group 2 and group 3 (all p values < 0.001). PostIOP30 values were similar in group 1 and group 2 (p = 0.261), but were lower in group 3 than other two groups (p < 0.001, p = 0.001, respectively). Vitreous reflux was identified as the only factor affecting postinjection intraocular pressure changes (p < 0.001), and a negative correlation was found between the total number of intravitreal injection and vitreous reflux (p = 0.032).

CONCLUSION

The major factor affecting short-term postinjection intraocular pressure elevation was vitreous reflux, and intraocular pressure levels increased as the amount of vitreous reflux decreased. Vitreous reflux and its amount decreased as the total number of intravitreal injection increased.

Patient safety and beyond: what should we expect from microneedle arrays in the transdermal delivery arena?

Research based upon microneedle (MN) arrays has intensified recently. While the initial focus was on biomolecules, the field has expanded to include delivery of conventional small-molecule drugs whose water solubility currently precludes transdermal administration. Much success has been achieved, with peptides, proteins, vaccines, antibodies and even particulates delivered by MN in therapeutic/prophylactic doses. Recent innovations have focused on enhanced formulation design, scalable manufacture and extension of exploitation to minimally invasive patient monitoring, ocular delivery and enhanced administration of cosmeceuticals. Only two MN-based drug/vaccine delivery products are currently marketed, partially due to limitations with older MN designs based upon silicon and metal. Even the more promising polymeric MN have raised a number of regulatory and manufacturability queries that the field must address. MN arrays have tremendous potential to yield real benefits for patients and industry and, through diligence, innovation and collaboration, this will begin to be realised over the next 3-5 years.

An arched micro-injector (ARCMI) for innocuous subretinal injection

Several critical ocular diseases that can lead to blindness are due to retinal disorders. Subretinal drug delivery has been developed recently for the treatment of retinal disorders such as hemorrhage because of the specific ocular structure, namely, the blood retinal barrier (BRB). In the present study, we developed an Arched Micro-injector (ARCMI) for subretinal drug delivery with minimal retinal tissue damage. ARCMIs were fabricated using three major techniques: reverse drawing lithography, controlled air flow, and electroplating. In order to achieve minimal retinal tissue damage, ARCMIs were fabricated with specific features such as a 0.15 mm(-1) curvature, 45° tip bevel, 5 mm length, inner diameter of 40 µm, and an outer diameter of 100 µm. These specific features were optimized via in-vitro experiments in artificial ocular hemispherical structures and subretinal injection of indocyanine green in porcine eye ex-vivo. We confirmed that the ARCMI was capable of delivering ocular drugs by subretinal injection without unusual subretinal tissue damage, including hemorrhage.